Comparative Study On Algorithms For Multi-objective Location-Routing Problem

Location-routing problem is an important problem in an integrated logistic system. In an integrated logistic system where decisions on location of depot, vehicle routing and assignment of routes to vehicles are considered simultaneously, accordingly improving the efficiency of delivery. Literature on location-routing problems addressed the location and vehicle routing decisions with a common assumption of assigning one route to one vehicle. However, by allowing multiple use of vehicles, further cost can be saved. So the notion of assigning several routes to a vehicle during the routing procedure is explored in our integrated model.Total cost and workload balance are common criteria influencing decision-making. This paper extends the equity criteria important to operational staff-workload balance (total trip times and load), and its tradeoff with the total cost. Based on this, we considere the multi-objective location-routing problem integrated with the routes assignment decisions, found corresponding mathematical model, and test the modol by Lingo program. Because the model is NP-hard, we analyse using metaheuristics of tabu search and simulated annealing to the problem, to examine the effect of the multiple use of vehicles under two versions: simultaneous or sequential routes assignment to vehicles. Simultaneity using the data that a telecommunication company offered to compare difference of algorithm performance, and adoptes the hypothesis testing of difference between two population proportions to compare two algorithms on the strength of their multi-objective solutions. Results show that the area characteristics is a significant factor in differentiating the performances between the two metaheuristic versions. In the area with long routes, the SA versions indicate better results than the TS versions under sufficiently long running time. In the area with shorter routes, the TS versions and SA versions indicate no significant differences in their results. The simultaneous versions have advantage over the sequential versions in problems where routes are capacity-constrained, but not in the time dimension. The simultaneous versions are also more effective in generating non-dominated solutions than the sequential versions.